The present invention relates to a method of testing and/or monitoring the system frequency of a microcontroller, and also relates to a microcontroller designed with the corresponding testing and monitoring apparatus, arrangement or structure.
In microcontrollers, it is believed that there have been problems in conjunction with checking the system frequency, because all the frequencies of the microcontroller system may be derived from a quartz oscillator assigned to the microcontroller. While a second frequency standard or a second quartz oscillator might be used, it is believed that this would be associated with additional costs and a greater complexity.
If problems occur with such a quartz oscillator, or if it fails completely, the function of the respective microcontroller or control unit may only be disturbed or cannot be maintained at all. If, for example, such a failure occurs in important automotive control units such as the engine control unit, it can lead to a complete operating failure of the motor vehicle.
In this regard, German Published Patent Application No. 197 22 114 refers to a clock signal producing device and use of a quartz oscillator.
The exemplary method and/or exemplary embodiment of the present invention is intended to make available the simplest possible method of testing and monitoring the system frequency of a microcontroller.
According to the exemplary method and/or exemplary embodiment of the present invention, the system frequency of a microcontroller may be determined without providing a second frequency, i.e. a direct frequency measurement. It is believed that this is because the working voltage of a voltage-regulated oscillator or VCO, which is used according to the exemplary method and/or exemplary embodiment of the present invention, is a measure of the frequency at which this oscillator oscillates.
The working voltage of the VCO may be expediently measured by an A/D converter. A digital signal made available through such an A/D converter may be coded in a suitable manner, so that a simple reference to the system frequency to be tested is able to be derived.
In another exemplary method and/or exemplary embodiment involving the exemplary microcontroller according to the present invention, the system frequency derivable from the measured operating voltage of the VCO may be compared with a clock frequency of a quartz oscillator assigned to the microcontroller. With such a comparison, it is believed that the clock frequency of the quartz oscillator may be easily checked.
In addition to the VCO and the A/D converter, the microcontroller may be expediently equipped with a quartz oscillator. It is believed that system frequencies may be checked very accurately with such a microcontroller.